Diabetes is a disease in which sugar accumulates in the blood of a patient because a hormone called insulin is not secreted enough by the pancreas or fails to work properly. Diabetes causes various complications, including high blood pressure, kidney failure, and damage to the eyes. Because there is no complete treatment for diabetes, a patient must maintain an appropriate glucose level in his or her blood through dietary treatment, exercise treatment, and the injection of insulin. For the management of blood glucose levels, accurately measuring blood glucose is essential.
To measure blood glucose levels, many methods exist, such as a method based on the reducibility of glucose, a method using a direct reaction of sugar in an acid condition, and a method using an enzymatic reaction of glucose. In addition, methods used in clinical medicine include a method in which blood drawn from a finger or a toe is made to react with glucose oxidase, the degree of coloring is measured by utilizing a coloring reaction dependent on the concentration of glucose in blood, and the measured degree of coloring is converted into a blood glucose level. However, these invasive blood sugar measurement methods require diabetic patients to endure the pain of blood extraction. Blood extraction is required multiple times a day and puts the diabetic patients at risk of additional problems, such as infection.
Accordingly, an electrochemical method is widely used to measure blood glucose. In this method, blood is drawn and made to react with an enzyme. A blood glucose level is then measured by measuring the amount of current flowing in response to a predetermined voltage applied to the blood. However, this method requires not only the pain of blood extraction for each measurement but also continually purchasing disposable strips for blood glucose measurement.
Many noninvasive blood glucose measurement techniques have been used. These techniques measure blood glucose levels by irradiating infrared light to the skin and then analyzing the degree of infrared light absorbed or scattered in the skin. However, measured blood glucose levels in this method may vary widely according to a number of different factors unrelated to a patient's glucose level, such as the measurement location on the skin, the temperature of the skin, etc. These techniques are thus not widely used.
There is therefore a need for noninvasive blood glucose measurements that accurately measure blood glucose levels despite varying environments.